Generally, in a vehicle, a driving force of an engine is transmitted to a transmission via a torque converter, and is transmitted to a drive wheel via one of a forward clutch and a reverse clutch received in the transmission, thereby allowing the vehicle to be in a traveling mode. The forward clutch and the reverse clutch are selected by a shift lever used to perform a forward/reverse switching operation.
A control system of a general automatic transmission includes a forward solenoid and a reverse solenoid of an electromagnetic switching valve for controlling a drive mechanism involved with a forward/reverse operation of a shift vehicle; and a control device for controlling the forward and reverse solenoids, wherein an operator selects a shift position by operating a shift lever provided in a driver seat, and the solenoids are controlled to be turned on or off on the basis of the shift position of the shift lever detected by a control unit, thereby realizing the speed stages such as a neutral, a forward/reverse, and plural speed stages.
However, in a case where the shift operation is erroneously carried out in a direction opposite to a vehicle traveling direction during a vehicle traveling mode, a transmission, an axle, or the like may be broken down by a high shock generated when a transmission gear is engaged in accordance with the erroneous shift operation. For example, in a case where the shift lever is switched from a forward range to a reverse range by an operator's erroneous operation during a forward traveling mode at a predetermined vehicle speed or more, a large load is applied to the vehicle.
Therefore, Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-249220) discloses an automatic transmission control device which prohibits a switching operation from a forward range to a reverse range in an automatic transmission when a vehicle speed detected by a vehicle speed sensor is not less than a predetermined reverse prohibiting speed and which adopts a vehicle speed using a gear ratio and a turbine rpm obtained from a turbine rpm sensor instead of the vehicle speed when the vehicle speed sensor is in an abnormal state.
Additionally, Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-138424) discloses a configuration in which it is determined whether a vehicle speed deceleration direction is abruptly changed when a shift lever is switched to an R range by an automatic transmission control device and the vehicle speed is faster than a reverse prohibiting speed so as to output a determination that a solenoid is in a reverse prohibiting abnormal state when the vehicle speed deceleration direction is abruptly changed and to output a determination that the solenoid is in a reverse prohibiting normal state when the vehicle speed deceleration direction is not abruptly changed. Accordingly, it is possible to determine an abnormal state by detecting a dangerous state where a gear is not normally engaged at the time of a reverse departure, and thus to improve security and maintainability by informing a passenger of the determination.
As described above, in a case where the gear of the automatic transmission is erroneously selected by the operator in a direction opposite to the vehicle traveling direction during the vehicle traveling mode at a high speed, the transmission, the axle, or the like may be broken down due to a large shock. Particularly, in an industrial vehicle represented as a cargo handling machine such as a forklift or a reach stacker and a construction machine such as a motor grader, a bulldozer, or a wheel loader, the forward/reverse switching operation is frequently repeated since the driving operation is carried out in many cases during a work, and thus an operator's erroneous operation may easily occur. For this reason, a vehicle for preventing the problem has been strongly demanded. Additionally, in the above-described industrial vehicle, since the operator needs to carry out the driving operation during the work, a vehicle has been demanded which is capable of appropriately controlling a vehicle movement without requiring a complex operation as much as possible.